== Description
   Format objects contain format information which is applied to a cell, or
   group of of cells, in an Excel object.
   
== Instance Methods
Format#align
   Returns the align property.

Format#align=(value = "off")
   Sets the horizontal and vertical alignment within a cell.  Vertical and
   horizontal alignments can be combined.  Valid arguments are:

   Horizontal: left, right, fill, justify, merge
   Vertical: top, vcenter, bottom, vjustify

   Text can be aligned across two or more adjacent cells using the merge
   property.

   The vjustify (vertical justify) option can be used to provide automatic
   text wrapping in a cell. The height of the cell will be adjusted to
   accommodate the wrapped text. To specify where the text wraps use the
   Format#text_wrap= method.

Formate#bg_color
   Returns the value of the background color.
    
Format#bg_color=(value)
   Sets the background color of a pattern.  Patterns are defined via the
   Format#pattern= method. If a pattern hasn't been defined
   then a solid fill pattern is used as the default.
    
Format#bold
   Returns the bold value of the format.

Format#bold=(weight)
   Sets the bold property of the font.  Values in the range 100..1000 are
   also valid. 400 is normal, 700 is bold and 1000 is very bold.  Some might
   even say, daring.

   You can also specify true or false, which sets the value to 1 and 0,
   respectively.

Format#border
   Returns the border format.  The default is 0 (no border).
    
Format#border=(int)
   Sets the border for a given cell.  A cell border is comprised of a border
   on the bottom, top, left and right.

   Valid arguments are as follows:
   0 - No border
   1 - Thin single border
   2 - Medium single border
   3 - Dashed border
   4 - Dotted border
   5 - Thick single border
   6 - Double line border
   7 - Hair border

   Also see the Format#top=, Format#bottom=, Format#left=, and Format#right=
   methods.

Format#border_color
   Returns the format border color. The default is black.

Format#border_color=(value)
   Sets the color of the cell borders. Valid values are the same as for the
   Format#color= method.

   Also see the Format#bottom_color=, Format#top_color=, Format#left_color=,
   and Format#right_color= methods.
    
Format#bottom
   Returns the bottom border value. The default is 0 (no border).

Format#bottom=(integer)
   Sets the bottom border of the cell. Valid arguments are the same as for the
   Format#border= method.
    
Format#bottom_color
   Returns the bottom border cell color value. The default is black.

Format#bottom_color=(value)
   Sets the bottom cell border color.  Valid values are the same as for the
   Format#color= method.
    
Format#color
   Returns the font color. The default is black.

Format#color=(value)
   Sets the font color of text within a cell (not the cell itself).  Any
   integer from 8..63 is valid.  The following strings are also recognized:

   black, blue, brown, cyan, gray/grey, green, lime, magenta, navy, orange,
   purple, red, silver, white, yellow
    
Format#fg_color=(value = "off")
   Sets the foreground color of a pattern or uses a solid fill pattern if
   a pattern has not been defined.
    
Format#font
   Returns the font name used for text. The default is "Arial".

Format#font=(font_name)
   Sets the font used. Excel can only display fonts that are installed on
   the system that it is running on. Therefore it is best to use the fonts
   that come as standard such as 'Arial', 'Times New Roman' or 'Courier New'.
    
Format#font_shadow
   Returns the font shadow value.

   Mac only.

Format#font_shadow=(value)
   Sets the font shadow property.  0/1 or false/true may be used.

   Mac only.
    
Format#italic
   Returns the italic property for the font. The default is 0 (false).

Format#italic=(value)
   Sets the italic property of the font.  

   You can also specify true or false, which sets the value to 1 and 0,
   respectively.
    
Format#left
   Returns the left border value for the format.

Format#left=(integer)
   Sets the left border of the cell.  Valid arguments are the same as for the
   Format#border= method.
    
Format#left_color
   Returns the left cell border color. The default is black.

Format#left_color=(value)
   Sets the left cell border color. Valid values are the same as for the
   Format#color= method.

Format#num_format
   Returns the numerical format for numbers.  The default is 1.
    
Format#num_format=(value)
   This method is used to define the numerical format of a number in Excel.
   It controls whether a number is displayed as an integer, a floating point
   number, a date, a currency value or some other user defined format. 

   The numerical format of a cell can be specified by using a format string
   or an index to one of Excel's built-in formats, e.g.

      format1 = Format.new(:num_format => "d mmm yyyy")
      format2 = Format.new(:num_format => 0x0f)
      workbook.addformat(format1)
      workbook.addformat(format2)

      worksheet.write(0,0,36892.521,format1) -> 1 Jan 2001
      worksheet.write(0,0,36892.521,format2) -> 1-Jan-01

   Using format strings you can define very sophisticated formatting of numbers.
   Assume each of these is separate and has been added to a workbook:

      format.num_format = '0.000'
      worksheet.write(0,0,3.1415926,format) -> 3.142

      format.num_format = '#,##0'
      worksheet.write(1,0,1234.56,format)   -> 1,235

      format.num_format = '#,##0.00'
      worksheet.write(2,0,1234.56,format)   -> 1,234.56

      format.num_format = '0.00'
      worksheet.write(3,0,49.99,format)     -> 49.99

      format.num_format = '£0.00'
      worksheet.write(4,0,49.99,format)     -> £49.99

      format.num_format = '¥0.00'
      worksheet.write(5,0,49.99,format)     -> ¥49.99

      format.num_format = 'mm/dd/yy'
      worksheet.write(6,0,36892.521,format) -> 01/01/01

      format.num_format = 'mmm d yyyy'
      worksheet.write(7,0,36892.521,format) -> Jan 1 2001

      format.num_format = 'd mmmm yyyy'
      worksheet.write(8,0,36892.521,format) -> 1 January 2001

      format.num_format = 'dd/mm/yyyy hh:mm AM/PM'
      worksheet.write(9,0,36892.521,format) -> 01/01/2001 12:30 AM

      format.num_format = '0 "dollar and" .00 "cents"'
      worksheet.write(10,0,1.87,format)     -> 1 dollar and .87 cents

      # Conditional formatting
      format.num_format = '[Green]General;[Red]-General;General'
      worksheet.write(11,0,123,format) -> > 0 Green
      worksheet.write(12,0,-45,format) -> < 0 Red
      worksheet.write(13,0, 0, format) -> = 0 Default colour

      # Zip code
      format.num_format = '00000'
      worksheet.write(14,0,'01209',format)
     
Format#outline
   Returns the outline property. The default is 0.

   Mac only.

Format#outline=(value)
    Sets outline property.  Accepts 1/0 or true/false, respectively.

   Mac only.
    
Format#pattern
   Returns the background pattern value. The default is 0 (solid pattern).

Format#pattern=(int)
   Sets the background pattern. Valid arguments are 0..18.

Format#right
   Returns the right border value. The default is 0.
    
Format#right=(int)
   Sets the right border of the cell. Valid arguments are the same as for the
   Format#border= method.

Format#right_color
   Returns the right cell border color. The default is black.
    
Format#right_color=(value)
   Sets the right cell border color. Valid values are the same as for the
   Format#color= method.
    
Format#rotation
   Returns the rotation value. The default is 0 (no rotation).

Format#rotation=(int)
   Sets the rotation of the text in the cell.

   Valid arguments:
      0 - No rotation
      1 - Top to bottom
      2 - 90 degrees counter-clockwise
      3 - 90 degrees clockwise

   Note that fractional rotation is not possible in the Excel 95 format.
    
Format#script
   Returns the subscript/superscript property. The default is 0 (normal). 

Format#script=(integer = 0)
   Sets the subscript/superscript property of the font.

   Valid arguments:
      0 = Normal
      1 = Superscript
      2 = Subscript
       
Format#shadow
   Returns the shadow property value. The default is 0 (none).

   Mac only.

Format#shadow=(value)
   Sets the shadow property of the font. Accepts 1/0 or true/false, respectively.

   Mac only.
    
Format#size
   Returns the font size. The default font size is 10.

Format#size=(size)
   Set the font size. Note that MS Excel adjusts the height of a row to
   accommodate the largest font size in the row.
    
Format#text_justlast
   Returns the justlast value. The default is 0.

   Only applicable to Far Eastern versions of MS Excel.

Format#text_justlast=(value)
   Sets the justlast value.  0/1 or false/true may be used here.

   Only applicable to Far Eastern versions of MS Excel.
    
Format#text_wrap
   Returns the text wrap value. The default is 0 (off).

Format#text_wrap=(value)
   Turn text wrap on.  Excel will adjust the height of the row to accommodate
   the wrapped text. A similar effect can be obtained without newlines using
   the Format#align= method.

   Accepts 1/0 or true/false as valid values.
    
Format#top
   Returns the top border value. The default is 0.

Format#top=(integer)
   Sets the top border of the cell. Valid arguments are the same as for the
   Format#border= method.
    
Format#top_color
   Returns the top cell border color. The default value is black.

Format#top_color=(value)
   Sets the top cell border color. Valid values are the same as for the
   Format#color= method.

Format#underline
   Returns the value of the underline property. The default value is 0 (none).
    
Format#underline=(value = 0)
   Sets the underline property of the font.

   Valid arguments:
      0/false - No underline
      1/true  - Single underline
      2       - Double underline
      33      - Single accounting underline
      34      - Double accounting underline
     
Format#strikeout
   Returns the strikeout value. The default is 0 (none).

Format#strikeout=(value)
    Sets the strikeout property. 
